Ramon, ORA-03113 is a "catch all" client error which tells you that
communication with the database server was either broken or could not be
established at all. The oerr utiity is, as expected, extremely helpful
Here is it what it says:

That, essentially means something like "the database side is not talking
to me". The error is usually on the database side. There should be files
with extenstions
like ".trc" and names like alert_<Oracle Sid>.log to help you out with
the
database side. Situation that Barbara has mentioned happened because the
second thread could not acquire it's rollback segments, so thread failed
to start.
Client process that was trying to contact the thread would, naturally,
receive
ORA-03113. Another situation is when you actually install OPS (RAC)
software without having the DLM (cluster manager) installed. If you
don't have OPS hardware, don't install the software because it's only
going to mess things up. This is as much guesswork as I'm willing to do
at 1 A.M.
Please, find the trace files and the alert log and come back with more
info.

--
Mladen Gogala
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Author: Mladen Gogala
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